1885.] Geology and Paleontology. 389 
On the ends of this bow are two clamps, Z L, for holding and 
steadying the sphere, B, when being moved or carried from place 
to place. The clamp screw, J, is turned so as to draw downward 
the bow, o o, between the fulcrums, 7 m, which causes the upper 
ends of the bow to clamp the sphere. Four clamps may be 
used. 
I think it will be plain to any one that the presence of the air, or 
the attraction of the earth, sun or moon will be equally exerted 
on the sphere, B, and the balancing weight (screw G). Also, 
_ that the difference in the weight of the sphere, 4, before the air 
is exhausted and afterward, is the weight of the air exhausted. 
Also, that the difference in the turn of the screw, G, from its 
position at sea-level, and any tried elevation above, to balance the 
sphere, is the comparative weight of the air at the two places. 
If experience should prove that the accumulation of dust and 
moisture on the sphere, B, will materially affect the weight 
thereof, it can be obviated by balancing the sphere, B, with an- 
other of the same surface and weight (exhausted air excepted), 
which can be moved to the right or left on the left end of the 
balance beam, c, by means of a screw similar to G, and have 
the number of turns recorded by a vernier on the balance beam. 
I have seen the mercurial barometer affected by the sudden 
opening or closing of a door in a tight room where the barome- 
ter was hung. I think I was not mistaken when I thought I saw 
it vibrate with the sudden dashing March winds which are strong 
enough sometimes to stagger a man as he walks. The plan I 
suggest will not be affected by these conditions if kept out of the 
wind current. It will be interesting to compare its action with 
the mercurial barometer anyway.— no. T. Campbell, Rockville, 
Ind., Fan. 24, 1885. 
Tue ERIBOLL CRYSTALLINE Rocks, — Nature contains two 
lengthy articles upon the crystalline rocks of the Scottish high- 
lands, the one from the pen of Archibald Geikie, the other a 
report by B. N. Peach and John Horne. It appears a fresh ele- 
ment of difficulty has been introduced into the geology of the 
Highlands. The crystalline schists which in Northwest Suther- 
land overlie fossiliferous Silurian strata, and which were believed 
companied by “thrust-planes” or horizontal pushings for- 
ward of the rocks on the up-throw side. The coast sections of 
Loch Eriboll show these dislocations clearly. Beginning with 
gentle foldings they increase until the order of the strata is 
reversed. In Durness, for example, the overlying schists have 
been thrust over westwards across all the other rocks for at least 
ten miles. Some of the overlying bands are Archean gneiss, 
others Silurian quartzite, and in one case a mass of the Upper 
